Rotary impact wrench



Sept. 26, 1961 w. F. SINDELAR l 3,00428 ROTARY IMPACT WRENCH Filed Feb. 23, 1960 5 Sheets-Sheet l Sept. 26, 1961 w. F. SINDELAR ROTARY IMPACT WRENCH 3 Sheets-Sheet 2 Filed Feb. 23, 1960 Sept. 26, 1961 w. F. slNDELAR ROTARY IMPACT WRENCH 3 Sheets-Sheet 3 F'led Feb. 23, 1960 4United States Patent 3,001,428- ROTARY IMPACT WRENCH William F. Sindelar, Cleveland, Ohio, assignor to Master 'Power Corporation, Bedford, hio, a corporation of Maryland Filed Feb. 23, 1960, Ser. No. 10,390

7 Claims. (Cl. til-52.3)

This invention relates to an impact wrench and more particularly to an impact wrench having an anvil and a rotating hammer wherein a part carried by the rotating hammer is intermittently brought into engagement with the anvil to impart rotary impacting blows to the anvil. The instant application is directed to an impact wrench of the type disclosed in my copending application Serial No. 806,852, filed April 16, 1959, wherein the impact wrench is characterized by a construction including cooperating cam surfaces for advancing the rotating hammer part toward the anvil and for withdrawing the rotating hammer part axially with respect to the anvil following an impacting blow.

Numerous expedients have been employed to convert the rotary motion of la driving motor to intermittent impact blows against an anvil carried by an output shaft. Generally a massive hammer is rotated by the motor and the energy of the rotating hammer is intermittently dissipated by rotary blows against an anvil carried by the output shaft. Some of the prior art devices have included an axially slidable hammer dog 'which is carried by the rotary hammer and is adapted to be moved axially in and out of the path of the `anvil portions. In some instances the hammer dog of the prior art was spring-biased or spring-retracted out of the path of the anvil portions. Such anrangements under certain operating conditions resulted in the Vtransmission of torque to the anvil shaft independently of the hammer dogs. Other prior art constructions have provided centrifugal means and fluid piston and cylinder arrangements to move the hammer dog into or out of the path of the anvil portions. The prior art efforts to move the hammer dog into and out of the anvil path with cam devices have not succeeded since such prior yart efforts have included a rotary drive to the rotary hammer operating independently of the rotary drive to the hammer dog.

The present invention utilizes cooperating clam surfaces on the anvil, hammer dog, vand driver parts of the impact wrench so as to eliminate the use of springs or centrifugal means or fluid pistons for moving the hammer dog axially during the impacting blows of the wrench.

lt is yamong the objects of my invention to provide an impact wrench having `a driving shaft rotated by a motor and a driven shaft to rotate la nut, bolt, or the like, wherein the driven shaft is provided with an anvil and wherein the driving shaft is provided with a rotating hammer having a hammer dog arranged to be moved in and out of the path of anvil lugs as` may be determined by the torque requirements of the nut or bolt and the; torque imposed by the driving shaft.

It is a further object of my invention to provide an impact wrench according to the preceding object wherein the rotating hammer dog and the` driving shaft and the anvil are provided with cams which move the hammer dog into the path of the lanvil lugs and withdraw the hammer'dog from the path of the anvil lugs.

t is a further object yof my'invention to provide an impact wrench `according to the preceding objects wherein the anvil is provided with a cam shaft to rotate therewith and wherein the hammer dog is moved in and out of the path oi the -anvil lugs by a ball interposed between a cam on the cam shaft and la cam recess on the hammer dog.

It is Va further object of my invention to provide an impact wrench according to the preceding objects wherein the input driver of the wrench is provided with integrally formed, radially projecting cam lugs and wherein each cam lug is provided with a face disposed at an angle with respect to the longitudinal axis of the wrench and wherein the hammer dog is provided with radially disposed openings to receive the cam lugs on the input driver and wherein the sides of the openings in the hammer dog are disposed at an angle with respect to the longitudinal axis of the wrench whereby the hammer dog is retracted from the anvil following an impacting blow of the hammer dog.

It is a further object of my invention to provide a wrench laccording to the precedingobject wherein the anvil of the wrench is operatively connected to a cam and -a hammer dog having portions to engage the anvil for impact is provided with a ball recess and wherein a ball carried in the recess rolls along the cam to advance the hammer dog and wherein the hammer dog portions are brought into contact with the `anvil for impact prior to the escape of the ball over the high point of the cam and inclined surfaces on the ball and in the recess exert forces elective to move the ball over the high point of the cam.

It is a further object of my invention to provide a wrench according to the preceding object wherein the anvil is provided with a cam shaft non-rotatably coupled thereto and wherein the cam shaft is provided with a cam cooperating with a ball mounted in `a recess within the hammer dog to advance the hammer dog axially into the path of the anvil lugs as the ball is carried rotatably and axially with respect to the cam Shaft.

Further objects and `advantages relating to etliciency in operation, ruggedness of construction, ease of service and long life will appear from Ithe following description and the appended drawings wherein:

FIG. l is an elevation of an impact wrench including the driving unit therefor made `according to my invention;

FIG, 2 is an exploded view showing the parts of the impact mechanism in perspective;

FIG. 3 is an elevation with the impacting mechanism in section of a wrench made according to my invention;

FIG. 4 is a showing of a developed section at the center line of the ball showing the ball recess and the cam employed to `advance the hammer dog into the path of the anvil;`

FIG. 5 is a plan view with parts broken away and in section showing the hammer dog in its retracted position with respect to the anvil and the driver element;

FIG. 6 is a plan view similar to FIG. 5 but showing the hammer dog in its advanced position with respect to the anvil `and the driver element;

FIG. 7 is a sectional view taken as indicated on the plane 7-7 of FIG. 5;

FIG. 8 `is a sectional view taken as indicated at 88 of FIG. 6; and

FIG. 9 is a diagrammatic sectional showing of the cam surfaces effective to advance and retract the hammer dog relative to the anvil.

Referring to the drawings, the impact wrench, indicated in its entirety in fFIG, l, is characterized by a motor housing 6 having `a handle portion Tand motor control members 8 and 8a. Mounted `at the forward end of the housing is the impacting mechanism housing 9 having the outer end portion l0 of the anvil projecting therefrom. The portion 10 is provided with a square or other polygonal shape suited to drive socket wrenches and the like.

The motor unit within the housing 6 is preferably an air motor which is reversible so as to rotate the anvil portion l0 in either direction. It will be understood by those skilled in the art that other reversible motors such as, for example, hydraulic motors, may be used for driving the impacting mechanism carried within the housing 9.

As illustrated in PIG. 3 the output shaft 12 of the motor vis splined as at 13 to` receive a similarly spiined portion I14 on the driver element indicated in its entirety as at l5. The exterior of the portion 14 of the driver element is cylindrical and is mounted within an antifriction bearing 16 carried within the end of the motor housing 6.

The forward end of the wrench housing 9 is provided with a bearing 17 within which the anvil 15 is journalled. The inner end portion of the anvil 18 is provided with an overhanging flange 19 and integrally formed with the flange are `three spaced anvil lugs 2i), 2l and 22. The

. radial side portions of the 4anvil lugs receive the impacting blow from radial faces on the lugs 24-26 on the hammer dog which is indicated in its entirety as at 23. lt will be noted that the lugs on the anvil are spaced 120 from each otheraud that the cooperating lugs 24, 25 and 26 on the hammer dog are similarly spaced and are proportioned so as to have a limited amount of angular rotation in the space between the lugs on the anvil. At the end of such angular motion the radial face on the lugs 24, 25 and 26 of the hammer dog 23 engage the cooperating radial faces on the lugs on the anvil so that each lug transmits a proportionate share of the torque and impact from the hammer dog to the anvil.

The anvil i8 is provided with a central bore Sli for a portion of its length and lthe bore 3@ receives the forward end of a cam shaft 31. The flange portion l@ of the anvil surrounding the bore 30 is provided with spaced hemispherical notches 32, 33 and 34. ri`he anvil shaft is provided` with hemispherical recesses similarly spaced as at 35, 36 and 37. During assembly the end of the cam shaft 31 is arranged within the ybore 36 of the anvil, locking balls 38, 39 and 40 are positioned in the cooperating hemispherical recesses on the shaft and within the bore 36 so as to lock or key the cam shaft 31 against rotation relative to the anvil. `It will be understood that such balls 38-40 also transmit end thrust loads to the bearing 16 through 4the cam shaft 31.

The cam shaft 31 is provided with an integrally formed cam indicated in its entirety as at 41. The cam is characterized by a radially `flat portion 42 which terminates in a pointed cam portion 43. rl`he end of the cam shaft 31 remote from the anvil is indicated at "44 and the cylindrical portion 44 of the cam shaft is rotatably mounted within the bore extendingrthrough the driver element 15.

The hammer vdog 23 is arranged to surround a portion of the cam shaft as best shown in PEG. 3 and when the cam shaft 31 is assembled with the hammer dog 23 and the anvil 1S, la ball 45 -is arranged within a recess 46 of the hammer dog 23. It will be observed that during the assembly the ball 45 is retained within the recess by the cam 41 on the cam shaft 3l. The hammer dog may thus rotate relative to the cam shaft without advancing the hammer dog as limited by the angular extent of the recess 46` and the low area 42 of the cam. The angular extent of the recess 46 in the hammer dog 23 for the ball 45 is illustrated in FIG. 8.

It will be observed that as long as the ball 45 is carried rotationally with respect to the ycam shaft and rides along the at portion 42 of the camv 4l, the lugs on the hammer dog will be in a retracted position with respect to the path ofthe lugs on the anvil. When, however, the ball '45 is carried along the cam 4l'and up the sloping sides of the cam to the point 43, the hammer dog 23 is advanced laxially so that the lugs on the hammer' dog yare rotated in the space between the lugs on the anvil.

AsV best shown in FIG.. 4, each end of the ball recess in the hammer dog is provided with a surface generally parallel to the slope of the cam surface on the anvil cam 41 at the time of impact. The ball 45 is shown in EEG. 4 at the time of impact wherein the center C of the ball is forward of the line LD across the opposing surfaces of the cam 41 and recess 46, respectively. The

line LD is a distance less than a diameter through the ball at center C. Accordingly it will be understood that the sloping surfaces in the cam recess 46'and the cam 41V exert a component tending to bias the ball 45 to the left as viewed in FIG. 4. VThe movement to the left of the ball 45 is due to the fact that pressure is applied across the ball at one side of the center and thus the ball is projected over the highest point of the cam. This projection or throwing of the ball occurs immediately following the impact engagement between part 22 on the anvil and part 24 on the hammer dog. The arrangement l have provided and as illustrated in FIG. 4 insures that the hammer dog may retract freely without drag after impact and that there will be no axial motion of the hammer dog at the time of impact.

That portion of the hammer dog 23 yadjacent the driver element l5 is generally cylindrical in outline and is cut away to provide an opening 'at the lower side thereof as indicated in FIG. 2 at Sil and at the upper side thereof as indicated at 51. Each of the openings 56 and 51 have side walls which are inclined or spiral with respect to the longitudinal axis of the wrench. The opening 5l is provided with a side wall 52 Iand an Opposite side wall 53. The side walls 52 and 53 are cut to provide spiral surfaces arranged to cooperate with complementary spiral surfaces on the lug 55 of the driver element 15. The opening 5G is similarly provided with surfaces to cooperate with spiral surfaces on lug 56.

In FlGS. 5 and 6, the lug 55 is shown disposed Vin the space or opening 51 of the hammer dog 23. The lug 55 is provided with spiral walls inclined with respect to the longitudinal axis of the wrench similar to the inclination at the sides of the opening 51.

The side wall 55a of the lug 55 is on a spiral which corresponds to the adjacent spiral face 52 on the hammer dog 23. Similarly the other face 57 of the lug 55 is shaped to conform to the spiral face 53 on the hammer dog adjacent thereto. It will be observed by reference to FIG. 6 that when the driver element 15 is rotated in the direction of the arrow 58, the spiral face 55aI will be brought to bear against the cooperating spiral face 52 and will exert a force having a component acting to move the hammer dog axially in the direction of the arrow 59. Accordingly, the hammer dog will move in the direction of the arrow 59 after the impacting blow has occurred and the ball 45 is free to move back onto the low surface area 42 on the cam 41. Conversely, if the driver element 15 is rotated in the direction of the arrow 60, the lug 55 will be moved relative to the hammer dog 23 as permitted by the space 51. This will bring the spiral face 57 on the lug 55 against the spiral face 53 on the hammer dog. A component of the force from the lug 55 is effective on the hammer dog through the spiral faces 53-57 and the hammer dog 23 is retracted in the direction of the arrow 61.

It will also be observed that when the hammer dog 23 is rotated in the direction of the arrow 60, the ball 45 will be carried up to the high point 43 of the cam and thus will advance the hammer dog 23 toward the anvil 18 in response to` rotation in either direction. Rotation clockwise (as viewed in FIG. 8) will result in the ball 45 being located at end 46a of the recess 46. Thereafter the ball 45 rides Vup the cam 41 to the top 43 thereof and an impact blow is delivered by the hammer dog (see FIG. 4).

The hammer dog 23l and the driver element 15, when assembled as above described, are telescoped within a rotating hammer indicated in its entirety as at 65. The forward open end of the rotating hammer 65 is notched or slotted axially as at 66, 67 and 68 to receive the lugs` 24, 25 and 26 on the hammer dog. The rotating harnmer 65 is relatively massive and the energy of rotation in the rotary hammer 65, by way of the slot and lugs 66-24, is imparted to the hammer dog 23fand thus is intermittently transmitted to the anvil in the form of impact blows.

To assemble the impact wrench, the cam shaft 31 is advanced through the borel in the hammer dog 23 andV thence the forward end of the cam shaft 31 is located within the anvil by balls 38, 39 and 40 as above described. The ball 45 is arranged within the recess 46 before the cam shaft is positioned, as shown in FIG. 3. The driver element 15 is then arranged `uponthe end portion 44 of the cam shaft 31 with the lugs 55 and 56 within the openings 51 and 50, respectively, in the hammer dog. Thereafter the rotary hammer 65 is moved forward around the driver element 15 and the hammer dog 23 with the axial slots in the rotary hammer receiving the lugs on the hammer dog. The assembly is then arranged within the housing 9 and the housing 9 is mounted on the motor housing 6 with the splines on the driver element engaging the splines on the motor shaft 12.

I have found that by providing an angie of about 36 on the slope of the cam 41, along with cooperating cam surfaces of 70 on the retracting cam surfaces, that an efficient mode of operation is obtained. As illustrated in FIG. 9 the cam 41 slopes relative to the radial plane normal to the axis of the wrench at about 36. As soon as the ball '45 has been projected over the top 43 of the cam' 41, the cam surfaces of about 70 on the hammer dog and the driver 55 are effective to retract the hammer dog so that the portion 26 on the hammer dog is out 0f the path of the portion 22 on the anvil.

During the normal drive of the impacting wrench, the driver element 15 turns so as to bring the radially disposed lugs 55 and 56 into engagement with the sides of the openings 50 and 51. The rotation imparted to the hammer dog 23 by the lugs 55 and 56 carries the ball 4S to one end of its recess 46. The ball 45 is then constrained to roll up the inclined face of the cam 41. This rolling motion of the ball advances the hammer dog 23 axially so that the lugs thereon are brought toward the anvil in the space between the lugs on the anvil. The ball escapes over the high point 43 on the cam at the time of impact between the hammer dog and the anvil and thereafter the hammer dog is retracted so as to move the lugs thereon out of the path of the lugs on the anvil.

Although I have described one form of my invention in considerable detail, it will be appreciated by those skilled in the art that numerous modifications may be made therein without departing from the scope of the invention as defined in the following claims.

What is claimed is:

1. An impact wrench comprising a driver element, a driven element having an anvil carried thereby, said anvil having axially projecting lugs, a hammer dog mounted for axial movement between said driver and driven elements in and out of the path of said anvil lugs, a first cam means including a spiral surface on said hammer dog and a cooperating abutting spiral surface on said driver element for rotating the hammer dog and retracting the hammer dog from the path of the anvil lugs away from said driven element and toward said driver element, second cam means connecting said hammer dog and anvil to advance the hammer dog into the path of said anvil lugs for delivery o-f an impacting blow to said lugs.

2. An impact wrench comprising a motor-driven driver element, a driven element having wrench socket portions at the end thereof remote from said driver element and an anvil at the end thereof adjacent the driven element, said anvil having projecting anvil lugs, a cam shaft carried by said driven element and projecting axially therefrom toward said driver element, a hammer dog surrounding said cam shaft and mounted for axial movement therealong in and out of the path of said anvil lugs, said hammer dog having axially extending openings adjacent said driver element, cam means comprising integrally formed axially extending portions on said driver element disposed within said openings on said hammer dog for rotating the hammer dog and retracting the hammer dog from the path of the anvil lugs, and cam means on said cam shaft and a ball cam follower on the hammer dog connecting the hammer dog to the cam shaft to advance the hammer dog into the path of the anvil lugs for delivery of an impacting blow.

3. In an impact wrench, a motor-driven driver element, a driven element having a polygonal portion at one end thereof and an` anvil at the other end thereof, said anvil having axially projecting anvil lugs, a cam shaft carried by said driven element and projecting axially therefrom toward said driver element, a hammer dog surrounding said cam shaft and mounted for axial movement therealong, said hammer dog having projecting lugs moved therewith in and out of the path of said anvil lugs, spiral `cam meansintegrally formed on said driver element and spiral cam follower means on said hammer dog for rotating the hammer dog and retracting the hammer dog lugs from the path of the anvil lugs, cam means on said cam shaft, said hammer dog having a recess, a ball in said recess engaging said cam means on. said cam shaft to advance the hammer dog into the path of the anvil lugs for delivery of an impacting blow.

4. An'impact wrench comprising a power unit having an output shaft, impacting mechanism mounted on said power unit comprising a driver element splined to said output shaft, a driven wrench element mounted co-axially with said driver element, said wrench element having a polygonal end portion for driving a wrench socket and an anvil portion having axially projecting lugs, said wrench element having an axial bore centrally of the anvil portion, a cam shaft mounted in said bore and keyed to the wrench element to prevent rotation of the cam shaft relative to the anvil, said cam shaft projecting axially from said anvil and having a cylindrical end portion journalled within said driver element, a cam on said cam shaft intermediate said driver element and said anvil, a hammer dog surrounding said cam shaft, said hammer dog having spaced axially projecting lugs adapted to be advanced with the hammer dog into the path of the lugs on the anvil, said hammer dog having a recess, a ball mounted in said recess and projecting inwardly therefrom into the path of said cam whereby rotation of the hammer dog relative to the cam shaft moves the hammer dog axially toward the anvil, said driver element having oppositely disposed driving lugs, said hammer dog having openings to receive said driver element lugs, cam surfaces on said driver element lugs and on said hammer dog openings to retract the hammer dog subsequent to an impacting blow.

5. An impact wrench comprising a driver element, a driven wrench element mounted co-axially with said driven element, said wrench element having a square end portion for driving a wrench socket and an anvil portion having three spaced axially projecting lugs, said Wrench element having an axial bore centrally of the anvil portion, a cam shaft mounted in said bore, spaced recesses in the bore and `in the cam shaft, balls in said recesses to prevent rotation of the cam shaft relative to the anvil and transmit thrust to the cam shaft, said cam shaft projecting axially from said anvil and having a cylindrical end portion journalled within said tubular driver element, a cam on said cam shaft forwardly of said driver element and rearwardly of said anvil, a hammer dog surrounding said cam shaft, said hammer dog having spaced axially projecting lugs adapted to be advanced with the hammer dog into the path of the lugs on the anvil, said hammer dog having a recess, a ball mounted in said recess and projecting inwardly therefrom into the path of said cam whereby rotation of the hammer dog relative to the cam shaft moves the hammer dog axially toward the anvil, said driver element having driving lugs, said hammer dog having openings to receive said driving lugs, cam surfaces on said driving lugs and on said hammer dog openings to retract the hammer dog subsequent to an impacting blow, a cupshaped rotary hammer mounted on said driver element,

the Walls of said rotary hammer having axial` slots therein to receive saidv hammer dog lugs.

`6. ln an impact wrench, a housing, an annular bearing at one end of said housing, a power unit at the other end of said housing having an output shaft, an anvil mounted in said bearing, said anvil having a polygonal portion at one end thereof and axially extending anvil lugs atthe other end thereof, a cani shaft secured to said anvil centrally thereof and projecting from said other end of said anvil, a driver element within said housing mounted on said powerV unit output shaft, a hammer dog surrounding said cam shaft, said hammer dog having opposed notches therein at that end of the hammer dog remote from the anvil, the marginal portions of said notches providing spiral faces, said driver element having integrally formed oppositely extending driver lugs disposed in said notches, the sides of said driver lugs having spiral faces arranged to bear against the spiral faces at the margin of the hammer dog'notches whereby rotation of said driver element exerts a force on said hammer dog having a component acting to retract the hammer dog with respect to said anvil.

7. In an impact wrench, a housing, an annular bearing at one end of said housing, a power unit at the other end of said housing'having an output shaft, a bearing carried by said power unit spaced radially from said output shaft, an anvil mounted in said annular bearing, said anvil having a polygonal portion at one end thereof and axially extending anvil lugs within said housing at the other end thereof, a cam shaft secured to said anvil centrally thereof and projecting within the housing, a driver element within said housing mounted on said powerunit output shaft, said driver being joumalled in said power unit bearing, a hammer dog surrounding said cam shaft, said hammer dog having lugs to engage said anvil lugs, said hammer dog having opposed notches therein at that end of the hammer dog remote from the anvil, the marginal portions of said notches having spiral faces, said driver element having driver lugs `disposed in said notches, the sides of said driver lugs having spiral faces arranged to bear against the spiral faces at the margin of the hammer dog notches whereby rotation of said driver element exerts a force on said hammer dog having a component acting to retract the hammer dog with respect to said anvil, and a rotary hammer surrounding said driver and hammer dog, said rotary hammer having axial slots to receive said hammer dog lugs.

References Cited in the lile of this patent UNITED STATES PATENTS 2,160,150 vJimerson et al May 30, 1939 2,539,678 Thomas Jan. 30, 1951 2,712,254 Schodeberg July 5, 1955 2,745,528 Amtsberg May 15, 1956 2,753,965 Koman July 10, 1956 2,825,436 Amtsberg Mar. 4, 1959 2,881,884 Amtsberg Apr. 14, 1959 2,940,565 Schodeberg June 14, 1960 FOREIGN PATENTS 1,057,422 France Oct. 28, 1953 UNITED STATES4 PATENT. OFFICE CERTIFICATE CE CORRECTION Patent NILl 370431,428 September 26, 196i William AI?o Sindelar It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Signed and sealed this 27th day of March 1962.,

(SEAL) Attest:

ERNEST W. SWIDER DAVID L.. LADD Attesting Officer Commissioner of Patents 

